The Constitution establishes the United States government and lists the powers of each of three co-equal branches. Each branch has powers that check or balance the powers of the others, ensuring no single branch can overwhelm and subsume the others. The states and the people retain any powers not specified in the Constitution.

Voting for Representatives

U.S. citizens 18 and over have the right to vote, although laws governing how you register to vote vary by state. Federal elections happen every two years on the first Tuesday after the first Monday in November. Every federal election decides every seat in the House of Representatives and about one-third of the seats in the Senate. The president and vice president are elected every four years.

Making Laws

Article I of the Constitution establishes the legislative branch of the U.S. government, which consists of the House of Representatives and the Senate. Only Congress has the power to make new laws or change existing laws. The 435 House members represent the states in proportion to their population, while the Senate is made up of 100 representatives -- two from each state. Bills concerning revenue must originate in the House. Any other type of law can start in either the House or the Senate, but must be passed by a majority vote in both houses before it can be sent to the president.

Enforcing Laws

Once a bill gets a majority vote in both the House and the Senate, it must be signed by the president before it becomes law. Article II of the Constitution outlines the powers and duties of the president, who serves as many as two 4-year terms as head of government, head of state and commander in chief of the armed forces. As head of government, the president has the power either to sign a bill into law or to veto it. Congress can override a veto with a two-thirds majority vote in both houses. As the chief executive, the president implements and enforces federal law. Federal agencies, led by people appointed by the president and confirmed by the Senate, create regulations to enforce federal law on a daily basis.

Interpreting Laws

Sometimes Congress and the president pass a law that conflicts with part of the Constitution or exceeds the powers it gives to the federal government. The judicial branch, established by Article III of the Constitution, interprets laws to determine how they apply in individual cases and whether the Constitution allows them. The Supreme Court is the highest federal court, and as such its interpretation of a law is binding on the lower courts. All federal judges are appointed by the president and confirmed by the Senate to serve life terms. This sets the courts apart from political or electoral concerns and allows judges to make objective decisions with an eye to justice rather than worrying about re-election.